In chemotaxis by Bacillus subtilis, the information that attractant has bound to chemoreceptors is transduced a along a pathway, which includes loss of methyl groups from the methyl-accepting chemotaxis proteins (MCP)s, and ultimately results in a transient increase of counterclockwise rotation by the flagella. It is very important to trace this pathway, to discover what proteins are involved and what their functions are. Isolation and characterization of mutants represents a powerful means for identifying these proteins. We propose to lysogenize SPBeta2del-2::Tn917 in or near the che region, obtain specialized transducing phages, and use these to carry out a complementation analysis of a large collection of chemotaxis mutants. We will carry out detailed mapping of mutants, including deletion mapping and ordering on the genetic map. We will isolate and characterize null mutants, MCP mutants, methyltransferase and methylesterase mutants, and, to identify protein/protein interactions, second-site "revertants." We will characterize mutants representing the various cistrons by a variety of biochemical and chemotactic criteria: the emphasis of our laboratory on the enzymology of methylation should prove helpful in analyzing defects in these mutants.